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34 .Nd Intel(R) Non-Transparent Bridge driver
36 To compile this driver into your kernel,
37 place the following lines in your kernel configuration file:
38 .Bd -ragged -offset indent
42 Or, to load the driver as a module at boot, place the following line in
44 .Bd -literal -offset indent
48 The following tunables are settable from the
51 .It Va hw.ntb.debug_level
53 The default value is 0, higher means more verbose.
56 The NTB allows you to connect two computer systems using a PCIe link if they
57 have the correct equipment and connectors.
60 driver provides support for the Non-Transparent Bridge (NTB) in the Intel S1200
61 and Xeon E3/E5 processor families.
64 driver hides hardware details, exposing memory windows, scratchpads and
65 doorbells via hardware independent KPI.
67 The hardware provides 2-3 memory windows to the other system's memory,
68 16 scratchpad registers and 14/34 doorbells to interrupt the other system.
69 On Xeon processors one of memory windows is typically consumed by the driver
70 to workaround multiple hardware erratas.
72 Tne NTB configuration should be set by BIOS.
73 It includes enabling NTB, choosing between NTB-to-NTB or NTB-to-Root Port mode,
74 enabling split BAR mode (one of two 64-bit BARs can be split into two 32-bit
75 ones) and configuring BAR sizes in bits (from 12 to 29/39) for both NTB sides.
77 The recommended configuration is NTB-to-NTB mode, split bar is enabled and
78 all BAR sizes are set to 20 (1 MiB).
79 This needs to be done on both systems.
87 driver was developed by Intel and originally written by
88 .An Carl Delsey Aq Mt carl@FreeBSD.org .
89 Later improvements were done by
90 .An Conrad E. Meyer Aq Mt cem@FreeBSD.org
92 .An Alexander Motin Aq Mt mav@FreeBSD.org .
94 NTB-to-Root Port mode is not yet supported, but it doesn't look very useful.
96 On Xeon v2/v3/v4 processors split BAR mode should be enabled to allow
97 SB01BASE_LOCKUP errata workaround to be applied by the driver.
99 There is no way to protect your system from malicious behavior on the other
100 system once the link is brought up.
101 Anyone with root or kernel access on the other system can read or write to
102 any location on your system.
103 In other words, only connect two systems that completely trust each other.